Late detection is the primary cause of poor survival rates from cancer. Nanotechnology-enabled assays can detect early markers of cancer with much higher sensitivity than current detection methods. Existing assays use fluorescent probes with organic fluorophores or quantum dots, both of which have limitations. Organic fluorophores have limited brightness and photostability, reducing sensitivity and effective signal quantitation. Quantum dots exhibit toxicity and irregular blinking as well as broad emission spectra which reduces the level of multiplexing possible. We will develop a new class of ultrabright and ultrastable fluorescence probes, Surface Enhanced Fluorescence (SEF) Nanotags, to improve the sensitivity of fluorescence-based cancer detection. Nanoengineering of the SEF-nanotags to place fluorophores near the surface of plasmonic nanoparticles increases the light emission by up to a factor of 100X and significantly increases probe photostability. SEF probes will be functionalized with antibodies engineered to target cancer markers. The SEF nanotags will interrogate an analyte-containing solution and be detected on a microarray of complementary chemotropes. The brightness, photostability, and detection sensitivity of the SEF-nanotags will be compared to existing probes. These ultrabright and ultrastable SEF nanotags are easily adapted to existing fluorescence-based cancer diagnostics with improved sensitivity.